United States President Barack Obama has left Washington for his familiar spot on Martha's Vineyard for a two-week summer vacation, which comes as the US is engaged in airstrikes against Islamic militant targets in Iraq.

Obama, along with wife Michelle, daughter Malia and dogs Bo and Sunny, arrived at a Coast Guard station on Cape Cod before heading to the island off the Massachusetts coast. The presidential motorcade wove its way around Martha's Vineyard before pulling down a secluded drive that led to the Obamas' rented vacation house.

The Obamas' youngest daughter, Sasha, was not on Air Force One, but the White House said she would be joining the family for part of the vacation.

The president spent just 30 minutes at the house before taking off for the golf course. Joining Obama for a round at the Farm Neck Golf Club were former NFL player Ahmad Rashad, NBA player Ray Allen, and Cyrus Walker, the cousin of White House senior adviser Valerie Jarrett.

Obama has spent at least part of his summer in Martha's Vineyard each year he has been president except 2012, when he was running for re-election. In an unusual twist, he's breaking up his vacation with a two-day return to Washington midway through the trip.

Obama's advisers have been cagey about why the president is returning to Washington, saying only that he plans to hold in-person meetings at the White House

The president typically keeps a low-profile on his annual summer vacations, making the occasional visit into town and playing several rounds of golf. But he will headline a Democratic fundraiser on the island Monday night.Before departing Washington Saturday, Obama told reporters that he was ready "to not have a suit on for a while."